Hi! I can’t understand using Previewer. (And I have to apologize my poor English.)
I use Adalo2.0, so I think this app can available in PC or Mobile Phone.
When I use Adalo1.0, it used to display a screen like a smartphone. However, when I switch to Adalo2.0, it suddenly becomes a desktop screen, and I can no longer debug it as a smartphone. Additionally, even when I try pressing the “Share” tab, the usual QR code does not appear.
As an alternative - you can use browser’s capabilities to view your app in different screen resolutions.
When you press “Preview” on the top right, the new browser tab/window is opened and you can see your app there. The app will change its appearance based on this window’s size. So you can either change the size of your browser’s window, or use Developer tools to view app in different resolution. In Chrome it will be “View” - > “Developer” → “Developer Tools”, and then enable the responsive view using the icon on a screenshot: